Many machines, including many dialysis machines, have pneumatically-controlled functions that are carried out using pneumatic valves, herein referred to as gas valves or air valves. In pneumatically-controlled dialysis machines, pressurized air can be used to control the flow of dialysate, to close safety clamps, and to carry out other important functions. Air valves that include a flapper mechanism controlled by an electromechanical solenoid are referred to as flapper valves and are used in some pneumatic dialysis machines.
To ensure patient safety, the pressures in pneumatically-controlled dialysis machines are checked often to see whether any pressure leaks have developed. Gaseous diffusion, for example, through rubber and plastic materials in a valve, can result in a constant low-level leak rate. Thus, some safety systems discriminate between such a constant leak rate and a leak rate of greater concern. An alarm system must be set at a threshold value that is just above such a constant leak rate, but even a constant leak rate can vary from valve to valve. Moreover, for any given valve, the constant leak rate can vary over time, for example, due to temperature fluctuations and altitude fluctuations.
When very small foreign particles settle between the flapper and the plastic housing of a flapper valve, small leaks can also develop. Despite using air filters to prevent foreign particles from entering a pneumatic system and its gas valves, some foreign particles nonetheless make it into the system. Particles as small as 100 microns or less, or 50 microns or less, can enter a gas valve, become stuck on the flapper, and cause a leak. The particles can also sometimes become embedded in the elastomeric material making up the flapper, especially when made of soft rubber.
Although a slightly leaking air valve resulting from foreign particle contamination may not pose a danger to a patient, if the dialysis machine cannot distinguish between such a leak and a truly dangerous leak, then the machine might shut down unnecessarily thinking the leak is more serious.
A need exists for a valve system for a pneumatically-operated dialysis machine, which can detect a valve leak caused by foreign particle contamination and automatically take action to fix it. A need also exists for a flapper valve system and method that include a self-cleaning mode to clean the valve flapper of foreign particles. A need further exists for a flapper valve system and method that can automatically detect a leak attributable to foreign particle contamination and carry out a self-cleaning mode in an attempt to clean the valve flapper.